Removal of pharmaceuticals by powdered activated carbon adsorption: Effect of particle size and point of addition

摘要

Endocrine disrupting chemicals, anti-microbial compounds, and other pharmaceutically active compounds, are ubiquitous in wastewater treatment plant effluents and in drinking water sources that are impacted by wastewater discharges. Powdered activated carbon (PAC) adsorption is one water treatment process that can effectively remove pharmaceuticals, but little information is available on factors that affect pharmaceutical removal by PAC. Objectives of this research were to evaluate 1) the effectiveness of different PAC types (coal based, wood based, lignite based) for pharmaceutical removal; 2) the effect of PAC particle size (as-received PAC and submicrometer-sized PAC or S-PAC) on pharmaceutical uptake rates; 3) the effect of solution pH on pharmaceutical removal; 4) the effect of coagulant addition on PAC effectiveness; 5) the effect of different PAC addition points on pharmaceutical removal. Batch kinetic tests and jar tests were completed with six pharmaceuticals [bezafibrate (BZF), diclofenac (DCF), ibuprofen (IBP), metoclopramide (MCP), sulfamethoxazole (SMX), trimethoprim (TMP)]. Removal of the weak acid SMX increased with decreasing pH and removal of the weak base TMP increased with increasing pH. Pharmaceutical uptake rates obtained with S-PAC were considerably faster than those obtained with as-received PAC. Timing of PAC addition affected pharmaceutical removal and finished water turbidity. The presence of aluminum hydroxide floc interfered with TMP removal, especially when PAC was added together with coagulant. When PAC was added during the flocculation stage, settled water turbidity was higher than when PAC was added either prior to or together with alum.